The present invention principally, but not exclusively, aims at realising a single package belt design without above mentioned cost raising disadvantages, which is composed of only a single element type, which has a relatively uncomplicated shape and a relatively low weight so as to maximise the amount of torque transmittable by the belt.
In this design the limbs are released of a hooking function, i.e. released from a function in aiding the elements to exit a pulley. In the known belt design this function implicate, taken in longitudinal view, an axial outward moment acting at the base, i.e. radially innermost part of a limb, which thus is required to be relatively broad. Presumably to reduce the weight of the element, in the known design the limbs have been cut off in axial width toward their radial outer end. In the current invention, in the absence of such function the limbs may be made of substantial less axial width, allowing the m to extend fully radially beyond the carrier. This is realised by allowing a free, i.e. unforced mutual insertion of element and carrier. Surprisingly departing from the underlying insight according to the invention that at an in between pulleys trajectory the belt may be trusted to assume an at least slightly radially inwardly curved shape by mutual contacting of the radial outer portions of the elements, whereby exiting of the pulley is effect by the elements mutually contacting.
A major advantage in the current design, apart from ease of assembly, is realised in that the power transmitting capacity is optimised by the reduction on overall limb width, particularly in relation to the nominal element width, implying the width of the element at the rocking edge, which is generally proportional to an axial width of the carrier. The measure according to the invention allows the saddle surface to be relatively increased, which is favourable since thereby the width of the carrier may be increased and accordingly its thickness reduced. This is particularly advantageous when the carrier is composed of a set of radially stacked endless rings. It being recognised by the invention that radial outer rings of such set tends to contribute less to the power transmitting capacity than the radial inner rings. A reduction in number of rings may then be favoured over a small increase in the axial width of the carrier. Moreover, the number of rings also has a large influence on cost. Particularly, in this respect, the width of the individual limbs at a level at or near the saddle surface is set at less than one-twelfth the axial width of said surface.
In a further development of the invention, the limbs are directed at least for a predominant part radially under an angle at least substantially conforming to the angle at which lateral side faces, or pulley contact faces, of the elements for contacting the sheaves of a pulley are oriented, i.e. so-called flank angle cone angle. In this manner an axially wide mutual-contacting basis is realised for the elements, promoting the stability of the belt current design. Such is particularly desired in view of a lack of mutual hooking function of elements and carrier.
In yet a further development of the invention, the limbs of the elements may be provided with a hooking portion as known per se. However, according to the invention it is provided at considerably beyond the carrier when in contact with the element, such that it may be introduced by mutual rotation about the longitudinal direction of the belt. By this measure a stable mutual contacting of the element's upper parts, both in a pushing and in a slack in between pulleys trajectory is realised, enhancing both a secure operation of the belt, and the torque transmitting capacity thereof. Again this support the limb design according to the invention having a small axial width favouring the axial width of the saddle surface. The measure according to the invention of realising a large width of the limb at some radial distance from the carrier favours good mutual contact of the elements upper parts. With such a design, most secure with the longitudinal play between the elements of the belt reduced to a minimum in conformance with the common practice in the known belts, the belt operates in a manner wherein mutual contacting of the element upper parts prevent the belt from disintegrating.
The present invention further aims at principally realising a single package belt design without above mentioned cost raising disadvantages, which is composed of the least possible number of element types, which has a relatively uncomplicated shape and a relatively low weight so as to maximise an amount of torque transmittable by the belt, while still responding in a good manner to the various functional demands for a belt. Such a belt is according to the invention realised by the feature of the limbs extending radially beyond the carrier, defining a recess open to the radial outer side of the element, allowing a free mutual insertion between the element and the carrier.
A belt comprising such features may be produced easily since no additional part is required as a retaining means. Surprisingly in the design according to the invention, the retaining means is achieved by favourably utilising and adapting some geometric features inherently present within a belt, being the adaptation of the ratio between a belt's total longitudinal play between its elements and the radial belt height above the rocking edge. The solution is based on the insight that at a slack in between pulleys portion of the belt, the most critical part in view of disintegration of the belt, the elements may block one another in a stable end position in which the relevant belt part is curved at least slightly concave. The solution takes account of the experience and insight that such slack part tends to buckle radial inward due to the clamping action at the pulley where the belt exits, which makes the belt, at least the elements thereof to tend to continue to rotate with the same pulley.
With the solution according to the invention favourably large values of longitudinal play between adjacent pairs of element within the belt may be allowed thus favouring the assembly of the belt when the element height above the rocking edge is made sufficiently large. The invention hereby may take advantage of the experience that only part of the said is present in the slack trajectory part, while moreover the portion of that play actually present in this slack trajectory tends to be distributed between pairs of adjacent elements.
Alternatively to the preceding solution, the described problem of maintaining the integrity of a so called single package belt is according to the invention solved by a feature which is here incorporated in addition to the preceding solution. In this feature, at least the majority of the transverse elements have a upper element part of which a radial outer end portion has a greater thickness than that of the said rocking edge, such that an array of elements pushed against one another with in said belt by mutually contacting with said end portions, assumes a stable arc-like shape. In this manner, at least at a pushing in between pulley's trajectory a so called cat's back-like. arc is achieved in the pushing part of a belt as arranged between two pulleys. Thus exiting of a belt from a pulley is enhanced, while the elements do not fall apart from each other or from the carrier since they are wedged in their position when observed, from side elevation. With the addition, or presence as the case may be, of such feature, the belt may at stand still of a transmission be incorporated without the presence of a pre-tensioning spring in a pulley, since the wedging feature prevents the elements located at a transmissions upper side with respect to the earth's gravity from assuming a position from which the belt may no longer deform to a desired rod like condition. In a slack trajectory part either at the transmissions upper or lower side, the wedging feature aids in assuming a stable inwardly curved end position of the slack trajectory.
Surprisingly the measure according to the latter aspect of invention again realises the integrity of the belt while obviating to application of the previously described known means for maintaining the integrity of the belt by positively or directly limiting the relative radial movement between the transverse element and the carrier. This provides for the possibility of applying a recess entirely open in radial direction, i.e. with even leaving away hook or locking parts. For achieving this effect, according to the invention only a small but noticeable amount of tapering of the upper element part is required. In this way favourable advantage is taken of the circumstance that a belt incorporates a significantly large number of transverse elements.
It is here remarked that in the context of the current description the height of the element is assumed to concur with the dimension of the belt in the radial direction when positioned in a circular shape, the width of the element concurs with the dimension of the belt in the transverse or axial direction and the thickness of the element concurs to its dimension in the belt's longitudinal direction, i.e. along the circumference of the belt.
The above proposed embodiments and aspects of the invention, either per se or in combination most favourably operate in combination with a carrier composed of a set of radially nested endless flat metal bands that are relatively thin.